1. Field of the Invention
This invention relates generally to the field of medical instruments such as dialysis machines, and more particularly to the process of disinfection of such instruments. Even more particularly, the invention relates to a method for disinfecting a line that is dead-ended in a medical instrument.
2. Description of Related Art
Dialysis machines are machines that are used for treating patients suffering from inadequate kidney function. The machines typically have an extracorporeal blood circulation circuit that withdraws blood from the patient into an arterial line, circulates the blood to a dialyzer filter, and then returns the blood back to the patient via a venous line. The dialyzer filter is a semi-permeable membrane that separates the patient's blood from a dialysate solution that is circulated on the other side of the membrane. Blood-borne toxins and excess water are removed from the patient's blood though the membrane and are carried away in the dialysate solution.
The extracorporeal circuit typically includes a blood pump that is used to pump the patient's blood through the arterial line, dialyzer and back to the patient via the venous line. A venous bubble trap is typically placed in the venous line, for the purpose of separating out any bubbles that may have formed in the blood. In most machines, the venous bubble trap includes a vent line connected to atmosphere. An air pump is also typically placed in the vent line. Operation of the air pump in either the forward or reverse direction changes the pressure in the venous bubble trap, thereby raising or lowering the blood level in the venous bubble trap.
After the end of the dialysis treatment, the entire machine is subject to a cleaning and disinfection process. In the situation where the blood tubing set, dialyzer and other fluid pathways in the extracorporeal circuit are reused instead of replaced, then of course the extracorporeal circuit must be cleaned and disinfected. Methods of achieving a high level disinfection of a dialysis machine, including the extracorporeal circuit thereof, are described in the patent to Rodney S. Kenley et al., U.S. Pat. No. 5,591,344, assigned to the assignee of the present invention Aksys, Ltd., the entire contents of which are incorporated by reference herein. Additional methods and procedures for hot water disinfection are claimed in U.S. Pat. No. 5,651,893, also awarded to Rodney S. Kenley et al., and assigned to Aksys Ltd.
When a fluid line that is to be disinfected comprises a tube through which water (or a solution containing disinfection chemicals) can be continuously circulated, achieving a required level of disinfection is relatively straight forward. For example, in a hot water disinfection process, heated water at a predetermined temperature is allowed to flow through the tube for a predetermined amount of time, such as circulation of water at 80 degrees C for one hour.
A particular fluid path in a medical instrument, such as a dialysis machine, may be designed such that fluids cannot flow through a tube segment, that is, in one end of the segment and out the other end. In the known prior art, achieving disinfection of such a fluid line has been problematical at best, and such "dead-ended" fluid lines have generally been avoided. For example, if chemical disinfection agents are used then there is a problem of adequately rinsing the fluid segment and removing all of the chemical agents. If hot water techniques are used, there is no way to flow water through the tube segment and maintain a constant high level disinfection temperature in the fluid segment.
The present invention overcomes these problems and provides methods and techniques for achieving disinfection of a "dead-ended" fluid path or line. The methods and techniques can be applied to a clean and rinse process, in addition to a disinfection process.